Millions of National Savings and Investments (NS&I) account holders will no longer be able to manage their money through the Post Office, the group has revealed.
The change is the latest step in NS&I's modernisation plan aimed at helping it cope with the rising number of customers accessing their money online, by post or over the phone.
Some 2.3 million people who hold Investment Accounts and 260,000 Easy Access Savings Account customers will be affected by the move.
From 2013, these accounts will only be accessible directly, although Premium Bonds will still be available at the Post Office.
NS&I chief executive Jane Platt said ending the Post Office deal was part of the group's plan to "simplify and modernise" its range of savings products.
She said NS&I had been trying to encourage customers to invest directly since 2007.
"At the same time, the Post Office has grown its own range of savings products," she added.